making a solar tube

[p cooper]

I fancy having a go at soething like these ( but down the side of the garage to put some light in a dark corner of the garden where the beans are trying to grow.

is an internal one you can buy

I dont want to spend £200 to try it out

any ideas for materials ? I cant find a concave lens for the top - perhaps a car headlight lens - Rovers and Corsas seem the most straightforward shape ?

Materials for the tube? a sheet of acrylic 3mm mirror mounted inside a frame? had a hunt for highly reflective lining material but havent come across anything.

we are also looking at other options - a convex safety mirror on the garage wall angled down has been surprisingly effective

[markzoom]

Line anyting with aluminium foil and it becomes a "highly reflective material". A sheet of frosted glass IS lots of convex/convave lenses,so is a funnel (kind of). M.K.

[andrewpreece]

Use aluminised mylar for a reflective lining. It is sold as survival blankets in Outdoors and Camping type shops. You can get deck prisms for boats at a chandlers, they come in rectangular and round shapes I think, don't know what they cost. You could maybe even make your own with a mould and resin.

Andy.

[Mark S.]

Mirrors are terribly poor for using light that way, you'd be better off buying some mylar from somewhere like growell.co.uk - can buy a metre for £2.50 and sticking it over the mirror.

Mark S.

[bigcat]

Dont make a tube unless you really need a tube, as they will cost you in light and materials.

There are 2 grades of aluminised mylar, one reflective, the other very reflective. The cheaper stuf is used for emergency blankerts, and is no use for light tubes, as its reflectance is inadeuquate. Light in tubes bounces many times, so its critical to use top reflectivity material and keep it clean.

An open mylar mirror would be much easier for garden use. White chippings on ground help a bit too.

NT